saga/seata-saga-engine/src/main/java/io/seata/saga/engine/expression/spel/SpringELExpressionFactory.java
<reponame>tyc1210/seata-1/*
 *  Copyright 1999-2019 Seata.io Group.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package io.seata.saga.engine.expression.spel;

import io.seata.saga.engine.expression.Expression;
import io.seata.saga.engine.expression.ExpressionFactory;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.expression.AccessException;
import org.springframework.expression.BeanResolver;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

/**
 * SpringELExpression factory
 *
 * @author lorne.cl
 */
public class SpringELExpressionFactory implements ExpressionFactory, ApplicationContextAware {

    ExpressionParser parser = new SpelExpressionParser();
    ApplicationContext applicationContext;

    @Override
    public Expression createExpression(String expression) {
        org.springframework.expression.Expression defaultExpression = parser.parseExpression(expression);
        EvaluationContext evaluationContext = ((SpelExpression)defaultExpression).getEvaluationContext();
        ((StandardEvaluationContext)evaluationContext).setBeanResolver(new AppContextBeanResolver());
        return new SpringELExpression(defaultExpression);
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    private class AppContextBeanResolver implements BeanResolver {

        @Override
        public Object resolve(EvaluationContext context, String beanName) throws AccessException {
            return applicationContext.getBean(beanName);
        }

    }
}